Going Cordless: Figuring out today's cordless toolsby Curtis Rist
Try carrying a circular saw up a ladder, and the shortcomings of a power tool with a cord quickly become obvious: the cord is easy to trip over, and more than one has ended up mangled by the tool to which it's attached. Electric shocks can be a problem, especially when working near water or in the rain.
No surprise, then, that manufacturers have long pursued the idea of cordless tools with all the ardor of a quest for the Holy Grail. The key lies not so much in designing the tools themselves after all, a circular saw is a circular saw but in designing batteries that can deliver the power needed to operate them. See cordless tools.
The cordless tools also extend the concept of portability. Because they don't need to be plugged into anything, it's possible to haul these tools far away from a power source whether that means into the woods to build a tree house, or out in the yard to build a shed. See cordless combo packs.
Know Your Battery
New NiMH Batteries
Since the nicad recipe appears to have reached its upper limits in terms of power output, tool makers are turning to nickel-metal-hydride batteries, which are called NiMH for short. Because they don't contain cadmium, NiMH batteries are considered more environmentally friendly than nicad batteries.
One common battery rating, known as the amp hr (Ah), measures battery pack capacity. This rating has been steadily rising for nicad batteries over the last five years, but now appears to have hit its limits at 2.0 Ah. By contrast, the NiMH batteries are already at 2.0 Ah, and batteries with ratings of 3.0 Ah will soon be on the market. At the moment, and for the forseeable future, the NiMH batteries cost more than the nicads. Another potential downside to the NiMH batteries, as compared to nicads, is that they offer 25 to 50 percent fewer recharge cycles.
Curtis Rist, a writer for This Old House magazine, parks his power tool collection in New York's Hudson River Valley.